Currently all hospitals are medicolegally compelled to monitor women in labor to assure fetal well-being. This is accomplished by detecting fetal heart sounds by ultrasound electronics, or by direct recording of the fetal electrocardiographic impulses by inserting a fetal scalp monitor by wire into the scalp. Both of these do no more than indicate the heart rate of a baby, which is one of the last things to change in a case where the baby is gradually being deprived of oxygen.
Direct measures of oxygenation of tissues are possible by light delivered through the skull, filtering out back reflections except those from beyond a certain depth (2 or 3 inches into the head) and monitoring the reflected light for enzymatic changes and the color-sensitive changes of blood to determine the degree of oxygen deprivation in the blood and tissues. This sophisticated technique is currently being developed in collaboration by the University of North Carolina and Duke University departments of Bio-Engineering and Surgical Trauma. It is currently under contract by the United States Navy.
The actual monitoring consists simply of sending a beam of light into the scalp by one glass fiber bundle and measuring the back-scatter of this beam returned by a separate glass fiber bundle. These fiber bundles need be only large enough to transmit sufficient light for penetration and back-scatter. The current prototype for adult trauma cases where there may be interference with oxygenation because of head, heart, or lung injuries involves a fairly stiff half-inch cable held to the head by a strap.